Well- from a business standpoint - I would go with Crested Geckos and here's why - the corn market is a nice one but it seems a bit flooded right now. I really don't know a lot about newts so I really can't give advice there- but as far as cresteds go here's why:
1. they are pretty darn easy to maintain as far as I have read/ heard
2. They have incredible "cute factor" going so they aren't a hard sell
3. I personally know a crested breeder who just increased his breeding stock from 10 to 60 just to meet demand in the Nashville area. I personally think Cresteds are a great species- cute, handleable, relatively easy husbandry in relation to other geckos, and popular at the moment. Plus who wouldn't want a bunch of those cuties around? I don't know how difficult they are to breed - I do know that a good CB pair could run you some decent bucks but I'm pretty positive it's under 300